The satellites amplifying systems, for example communication or navigation satellites, are used in their zone of optimal efficiency, giving rise, in fact, to a power response that turns out to be non-linear.
These non-linearities cause power spread (inter-modulation products) that are outside of the useful band, or “spurious”, that have to be filtered at high power, so as to adhere to frequency regulations.
Hence, the implementation of such processing increases and complicates the payload of the satellite, both in terms of mass and volume.
Techniques are known for linearizing the amplifier by use of signal digital predistortion, at generation of the signal, such as illustrated for example by in U.S. Pat. No. 6,549,067 B1, the disclosure of which is incorporated by reference in its entirety.
Such embodiments impose a high bandwidth for the RF stage or radiofrequency stage, thus entailing a strong impact in terms of payload of the satellite.
Techniques are also known based on hardware linearizers carrying out compensation of the non-linearities at the input of an amplifying device by emulation, in phase opposition of the non-linearities, power-wise, notably by means of diodes, such as illustrated for example by the French Patent Application Pub. No. FR 2 722 350 A1, the disclosure of which is incorporated by reference in its entirety.
Such embodiments are rather ineffective for the transistor-based amplifiers commonly employed on satellites.